Color photography



y 9 -c. SCHETTLER EI'AL I 2,353,506

COLOR PHOTOGRAPHY Original Filed Jan. 22, 1940 s Sheets-Sheet 1 #W' 4' r ATTORNEYS July 11, 1944.; c. SCHETTLER EI'AL. 2,353,506

COLOR PHOTOGRAPHY Original Filed Jan. 22, 1940 3 Sheets-Sheet 2 HII July 11, 1944. c, sc R ETAL 2,353,506

COLOR PHOTOGRAPHY Original Filed Jan. 22, 1940 '3 Sheets-Sheet '5 AT ORNEYS Patented July 11, 1944 2,353,506 COLOR PHOTOGRAPHY Charles Schettlen and Erich F. T. Schenk, Miami, Fla.

Original application January 22, 1940, Serial No.

314,995. Divided and this application September 1, 1942, Serial No. 456,860

9 Claims.

This invention relates to color photography and one of its objects is to provide a photographic print in colors to be viewed by reflected as distinguished from transmitted light, in which the various color densities will be reproduced with greater fidelity and brilliance than is possible with methods heretofore used, and in accomplishing this we make use of image forming light reflective white particles distributed in varying amounts of concentration and depth within a medium which itself may be multi-colored to refiect the incident light, or a separate multi-colored filter is used in cooperation with said white particles. This invention relates more particularly to the method involved in the production of such' color prints, this case being a division of our application, Serial Number 314,995, filed by us on January 22, 1940.

Other and further objects and advantages of our invention will be apparent from the following description of it, taken in connection with the accompanying drawings in which Fig. 1 is a greatly enlarged cross sectional view of a multi-colored screen film at one stage of operation and a diagrammatic representation of the several steps involved in arriving at that stage.

Fig. 2 is similar to Fig. 1 showing said film at a subsequent stage of operation.

Fig. 3 is similar to Figs. 1 and 2 showing said film at a further stage of operation.

"Fig. 4 is a greatly enlarged cross sectional view of the multi-colored screen film of Figs. 1, 2 and 3 at a further stage of operation.

Fig. 5 is similar to Fig. 4 showing the said film in'its final form.

Fig. 6 is a greatly enlarged cross sectional view ofan assembly of films used in a modified form of the invention.

Fig. 7 is similar to Fig. 6 showing said films upon the completion of the operations.

Fig. 8 is a face view greatly enlarged of one form of the multi-colored filter shown in Figs. 6 and '7. r

Fig. 9 is a greatly enlarged cross sectional view of a modification of the film assembly shown in Fig. 6.

Fig. 10 is a greatly enlarged cross sectional View ofv a modification of the film assembly shown in Fig. 9.

Fig. '11 is a greatly enlarged cross sectional view of the multi-colored screen film of Fig. 1 before exposure, but of a somewhat modified construction.

1 In carrying out our invention, we make use and in the emulsion layer ll.

The layers H and 12, instead of being formed separately, may consist of a single layer 21 (Fig.

11), to which the color pattern 28 may be applied by dyes which partially penetrate the emulsion to a substantial depth, or again, the layers II and IZ'may be provided by an assembly of two films each having its own independent transparent support. 7

The final photographic print to be produced in accordance with our invention may involve the well known combinations of two, three or more colors, and if, as we prefer, a three color process is used, the colors of the emulsion l2 are preferably red, blue and yellow. The dyes used for producing the said multi-colored emulsion l2 should be such that the colors will not be affected by the chemicals used in the processing to be done later, or they may be such that one or more of the colors will be changed to the desired colors in the course of such processing. For instance, a dye of a different color can be used for the yellow portions of the emulsion filter in order to secure, in

a given instance, a better separation of colors during exposure, and the said portions later changed to the desired yellow color. The light sensitive particles of silver salts in the filter emulsion layer l2 need not be sensitive to all colors but should be sensitive to the respective colors in which they are embedded.

The scene or objects l3 which are to be reproduced in their natural colors in a print in accordance with our invention are first photographed separately and successively through a red, a blue and a green filter, designated in Figs. 1, 2 and 3 by the numerals [4, Ma and Nb, and from the three black and white color separation negatives I5, I51]. and 15b thus obtained, a set of three transparent black and white separation positives l6, 16a and l6b are then successively printed on the film 9 either by contact or projection with an appropriate color filter N, Na and l'lb interposed in'the light path and with the film 9 positioned so that the multi-colored emulsion filter side of the film 9 is towards said positives, or in other words the layer I2 is between the layer II and the light source. A blue filter I1 is 7 used in printing from the positive l6 of a negative 55 made through a red filter H8. A green filter iia is used in printing from the positive lfia of the negative Ia made through a blue filter, and a violet filter Ilb is used in printing from the positive I617 of the negative I5b made through a green filter Ib. It is obvious that care must be Figs. 1, 2 and 3, respectively. Where, as is shown in Fig. 1, the scene It is composed of different colors, such as violet, blue, green, yellow, orange and red, as well as white, light gray, dark gray and black and is photographed through the red filter i i; the color separation positive l6, made from the negative !5 will appear substantially transparent in the areas upon which the white,

red, orange and yellow colored images fell. due

to the presence of practically no converted me tallic silver in these areas, the black, dark gray andlight gray images will be represented by relatiye degrees of density in said positive, and the blue, green and violet images will appear as half tones or midway between transparent and opaque. Thispositive is then printed on the film 9 through a blue filter l1 and the various amounts of blue light produced by the various densities of the said positive it will affect substantially only the silver salts in the film 9 embedded in the blue dyed portions in the emulsion l2 and in those portions of the panchromatic emulsion ll immediately behind said blue dyed portions to a depth and concentration inversely proportionate to the various densities of the said positive I6. The color separation positive Mia printed from the negative ifsq obtained by photographing the same scene is through a blue filter Ma will appear substantially transparent in the areas upon which the white, red, blue and violet images fell due to the presence of practically no converted metallic silver in these areas, the black, dark gray and light gray images will be represented by relative degrees of density in said positive, and the orange, yellow and green images will appear as half tones ormidway between transparent "and opaque. This positive is printed on the film 9 through a green filter Ila and, the various amounts of green light produced by the varyingdensities of the said Positive Ilia affect substantially only the silver salts in the film 9 embedded in the yellow dyedzportions in the emulsion I2 and in those portions of the panchromatic emulsion ll immediately behind said yellow dyed portions to a depth and concentration inversely proportionate to the various densities of the said positive 16a. The color separation positive I612 printed from the negative [5b obtained by photographing the same scene l3 through a green filter Mb will appear substantially transparent in the areas upon which the white, yellow, green and blue images fell due. to the presence of practically no converted metallic silver in these areas, the black, dark gray and light gray images will be represented by relative degrees of density in said positive, and .therred, orange and violet images will appear as half tones or midway between transparent and opaque. This positive is printed on the film 9 through a violet filter lib, and the various amounts of violet light produced by the various densities of the said positive It?) will effect substantially only the silver salts in the film 9 embedded in the red dyed portions of the emulsion l2 and in those portions of the panchromatic emulsion H immediately behind said red dyed portions, to a depth and concentration inversely proportionate to the various densities of the said positive I611.

The aggregate effect of these several operations on the film 9 when it has been developed and fixed is that the depth and concentration of the particles of converted metallic silver in the emulsions H and I2 vary in accordance with the various intensities of the light transmitted onto the film through the three color separation positives and their accompanying filters. In some instances only the silver salts in the emulsion filter 12 have been affected and then to different extents, while in other instances the light has beenintense enough to afiect not only the silver salts embedded in the related colored portions of the emulsion l2 but also those embedded in the portions of the panchromatic layer l l behind them. It will be understood, of course, that known methods of control both in the making of the color separation negatives and positives and the printingof said positives on the film 9, such as the time of exposure, the time of dev lcnmen and oth r factors known and reco nized in the photographic art, must be exercised in order to secure a proper contrast and density in the film 9. j

. The film 9 is next treated so as to change all the black metallic silver particles that remain in the panchromatic emulsion layer H and the multi colored emulsion filter I2 into substantially white colored particles, which may be done by;

immersing said film in a suitable bath, such as the following:

Ammonium chloride gr Mercury bichloride gr 112 /2 Water oz 8% which will convert" the black silver into white particles, as shown in Fig. 4.

I By the term white, however, we do not wish to confine ourselves to a pure white. Although the whiter the particles can be made the better the final; results will be, providing thereby an increase of light reflectivity, but for this purpose a; near-white is sufficient. Our use of this. term,

therefore, includes a shade approaching white and one that does not possess any color tint which wouldsubstantially alter the colors of the light reflected from the multi-colored filter l2 so as, to interfere with the faithful reproduction of the colors of the original scene or objects photographed. It, may be noted that if the exposure cannot give the desired control, the film canfirst be reduced to proper density and after a thorough washing the .film may be subjected to the bath mentioned above. 7

As a final step, it is necessary to give the film 9 a, backing of; a lighteabsorptive and n onreflective quality (since the film is. to be viewed through the transparent support Ill, the surface contain- 7 ing the multi-colored emulsion filter l2 will constitute. the back. of. said film); and this backing maybe applied many one of several ways, for instance, by a chemical such as a redeveloper'in which the film. may be immersed for a short period just suificient to; blacken the white parti: cles lying just below the surface of the multicolored emulsion filter l2, the result of which is shown in Fig. 5, or by applying a black. dye to said surface and allowing it to sink in to but a slight depth, or by cementing the film to asheet of black opaque paper., The picture is viewed through the transparent support II). For purposes of clarity Figs. 4 and 5 show the film 9 in juxtaposed relation tothe scene or objects, l3 which it represents. Either of the last two methods of providing the backing may be found to be preferable in the absence of sufficient silver particles in certain areas to provide a substantially complete black backing, such, for instance,

where the image is that of a black object which produced but little actinic effect upon the silver salts.

It will be noted that it is the opaque white particles and their relative distribution throughout the film that gives form and color to the picture. For instance, if neither of the emulsion layers contained any of said white particles, theoretically no color would be reflected from the film since the black backing would absorb all the incident light. On the other hand, if the white particles were present in maximum density in the panchromatic layer the film would present merely a plain white surface. This is a condition that might obtain if the intensity of the printing light through each of the threefilter colors above described was such as to afiect all the silver salts in the panchromatic emulsion layer so as to provide no interstices between them to allow the passage of light to and from the white particles in the multi-colored emulsion filter [2. The greater the amount of white particles in the emulsion filter [2 the lighter will appear th respective colors in which they are embedded and these varying tones of color may thus extend all production of a photographic print in color.

A modified form of our invention differs from the foregoing in that the material to constitute the finished color photograph, instead of such as the film 9, is, as shown in Fig. 6, made up of three units comprising a thin sheet I!) of transparent material, such as Celluloid, Cellophane, glass or th like which is variously colored, such as blue, red and yellow in a minute pattern of lines, squares, mixed dots or the like to form a multi-colored filter, the pigments used being of a permanent character which will be unafiected by any subsequent processing to which the photographic emulsions to be attached thereto are subjected. To one side of the sheet I9 is detachably secured by a transparent cement or otherwise a sheet of panchromatic film of a standard type comprising the support 20 and the emulsion 2|. To the opposite side is similarly secured another sheet of standard panchromatic film comprising the support 22 and the emulsion 23. In practice we have-found it advantageous, although not necessary, that the emulsionlayer 23 be somewhat thinner than the emulsion layer 2|.

3 This triplex unit is subjected to the same p cedure in practicing our invention as the film ,9, as hereinbefore described, in respect to the successive exposures to the color separation positives throughtheir respective accompanying filters. When the films on the. opposite sides of the color filter sheet 19 consist of similar panchromatic films -either film may be positioned towards the color separation positives, but where their respective emulsions are of different thicknesses the film having the thinner emulsion 23 should be. positioned towards the said positives. After the exposures have been completed, the two films are separated from each other, and the one that was on the side towards the color separation positives duringtheexposures is developed by a reversal process to change it from a negative to a positive. The other film that was on the opposite side of the color filter sheet l9 away from the color separation positives is developed, fixed and washed, after, which it is treated,

as hereinbefore described, ,with respect, to the,

film9, to change the black. silver particles to a white color. The said two films and said multicolored filter are then reassembled permanently in their former position in exact registry with one another. A white light reflective backing 24 is applied to the film havingthe emulsion 23, which may be a white cardboard mount, leaving the picture to be viewed through the film having the emulsion 2 I. The result of this modified process is shown in Fig. "T and provides a photographic color print'i'nfwhich the emulsion 23 in connection with the multi-colored filter will produce'all the shades ofthe filter colors darker than said colors themselvesextending downto black, while the emulsion 2| will at the same time produce, in accordanc with the different degrees of density of the white particles, the several colors extending from normal up to white, and the combined effect will be to give af'aithful color reproduction of the original scene photographed.

It is obvious that the assembly shown in Fig. 6 may be variously composed; for instance, instead of two separate films, each comprising a support and an emulsion, placed on either side of a multi coloredfilter, the multi-colored filter may form the support for one of said emulsions, for instance, the emulsion 23, as shown in Fig. 9, the other emulsion 2| having its own independent support, or the multi-colored filter may form the support for both emulsions, as shown in Fig. 10. In the latter case; since each of the emulsions is to be subjected to different treatments, it will be that both emulsions maybe given the same treatment, and the emulsion that was positioned to- ,wards the color separation positives may be afterwards treated by applying to it a blackening solution, such as a developer with a brush or swab, to restore the white particles in that emulsion to their original black color. Where separable films are used the final white reflecting backing may be provided by not making the film having the emulsion 23 a reversed positive butdeveloping it as a negative and printing it on another film having a white refiecting' back. Where the two emulsions form separable film units as shown in Fig" 6, they may-also be exposed separately, and, with the aid-of registration marks placed thereon andmaintained throughout the various steps, the several units may be satisfactorily matched in their final assembly, the obviously necessary care being taken to keep the apparatus and other items in the same position throughout the various steps." r

In the preparation of the multi-colored filter t9, particularly when the tiny colored areas are in-the form of round dots or other shapes so that one is not contiguous to others throughout its perimeter but uncolored areas are interpersed among them, we have'found that such uncolored orclear areas permit many rays of light unfiltered by the filter l9 to fall upon the emulsion 2! during exposure and therefore produce in the final result a greater amount of white particles than would otherwise obtain and upset somewhat the color balance in' the print relative to the colors ofthe origina'l'scene or objects. To remedy this condition in the case of such a filter we fill the areas between such colored dots, 25, as shown in Figz8, with an opaque water soluble substance indicated by the numeral 26, so that during the exposure the only "light that reaches the emulsion 21 is that which passes through the multi-colored dots comprising the filter 19. In the subsequent processing this substance is dissolved out leaving said areas 26 clear and transparent Other methods may be used to render the said areas opaque during exposure. fFor instance, the filter i 9. may have applied to it' an emulsion adapted for the well-known wash-on gelatine' reliefmethods; such as, for, instance, a bichromatedigelatine, which is'then exposed to light from the other side. The result of this will be tqj-hardenthis gelatine emulsion in the areas between the colored dots of the filter while the areas in register with the colored dots being less exposed, may be washed out,jleaving thegelatin'e in relief behind the said intervening areas. "In

doing this it may b advantageous to make use of an additional filter to amplify the relative hardening of the gelatine between the intervening clear areas and those in register with the colored dots. ,The hardened relief portions of the gelatine corresponding to the said. intervening clear areas may be then rendered'opaque' by the application of a suitable .water soluble pigment,

and the filter 1'9 is then ready for use in making the exposures as above described, after which these opaque areas may be then washed out leaviiig these areas clear and. transparent.

Another method for thus preparing the filter l9 would'be' to expose a separate film through thefilter l9. and so that the resultant negative would have a high degree of density, approxi-v mating complete opacity, only in the areas corresponding to the intervening clear areas in the filter and the negative thus produced'rnay be used asa mask in conjunctionwith the colored dot filter in making the exposures, after which it is discarded'in assembling thefin'al print; vIn stead of a'separatefilm'being used to constitute such a mask it'maybe, an emulsion applied to thecolored dot filter, which after the exposures have been made may be, stripped off. I

j These clear areasin the multi-colored filter l9, although very small in comparison with the col- Qred areas, have an advantage in that they not only'obivate'. the presence of darkspotsin the finished print caused by an excess of the opaque whit rticlesin theemulsion 2| in these areas,

but also add to the brilliancy of' the finished print, since the incident light passing freely through said clear areas'will in a large measure be reflected back through the colored dots in the filter l9. r I

Afurther modification of our'invention would be tosubstitute'for the emulsion 2 I, one such as is used in the wash-off gelatine relief process, for'iris'tance', a bichromated gelatine, having embedded therein a mass of minute opaque white particles uniformly dispersed throughout the gelatine and of a material that will not be affccted by the subsequent steps of the wash-ofi relief process, except that they will wash ofi with the portions of thegelatine inwhich they are embedded. After the exposure through the filter [9 as above described and the washin -off of the parts of the gelatine which have not beenhardened, the remainder of the gelatinelayer and thesaid white particles embedded therein will have similar characteristics to the silver emulsion 21 after the black silver particles have been transformed to white particles as herein before described. Again, the emulsion 2| may be one containing silver salts which after the exposure is separately developed as a negative. From this a positive print is made on a film provided with the saidgelatine layer containing the said white particles, which is then processed by the Wash-off relief method. This print 'is-then assembled with the filter l9 and the positive film 22-23 and mounted one. light reflective support .24 as'above described, to constitute the finished print. I

. It is obvious that many other changes may be made in our invention without departing from the spiritthereof as defined inthe appended claims, and while we have described our invention in connection with a three color process, it is obvious that it is applicableto a two color process or to one utilizing more than three colors:

What we claim is: i

1. The method of making a photographic color print to be viewed by reflected light which -in'- cludes the successive steps of exposing a sensitive film provided with a sensitive inner layer of a silver salt emulsion and a' sensitive outer layer composed of a transparent additive color-screen filtersilver salt emulsion, through said colorscreen filter to a/series-of color separation photo graphic images with light of difierent colors, developing and fixing said film, and converting the metallic silver image to a substantially white image. 2'. The method of making a photographic color print which includes the steps of exposing a sensitive film provided with an inner layer of "a panchromatic emulsion and an outer sensitive layer composed of a transparent additive colorscreen filter silver salt emulsion through said color-screen filter to a series of color separation photographic images with light of different colors, developing and fixingsaidfilm, converting the metallic silver image to a substantially white image and mounting said film emulsion side down upon asubstantially black backing. 1

3. The method of making a photographic color print upon a light sensitive film composed ofa' panchromat c emulsion and an overlying layer' consisting of .a .light'sensitive transparent addi-' tive color-screenfilter emulsion, which includes expcsingsaid film through 'said'color-screen filter to a, series; of color ffseparation photographic images with light or difierent colors, converting the image defining particles contained in said emulsions after developing and fixing, into substantially white particles, and applying to the outer side of said color-screen filter emulsion a substantially black backing.

4. The method of making a, photographic color print which includes exposing a panchromatic film which throughout the length and breadth and for a substantially uniform portion of the thickness of its emulsion layer consists of a transparent additive color-screen filter, through said color screen filter, successively to light of different colors, developing and fixing said film, converting the silver particles contained in said film into substantially white particles, and applying a substantially black backing behind the colored face of said film.

5. The method of making a photographic color print to be viewed by reflected light which includes exposing a sensitive film provided with an inner layer of panchromatic emulsion and a sensitive outer layer of a silver salt emulsion in which is embodied a transparent additive color-screen filter, through said color-screen filter, to a series of color separation photographic images with light of different colors, developing and fixing said film, converting the metallic silver image to a substantially white image and applying a substantially black backing behind the emulsion side of said film.

6. The method of makin a photographic color print which includes the steps of exposing a sensitive film provided with an inner layer of a panchromatic emulsion and an outer sensitive layer composed of a transparent additive colorscreen filter silver salt emulsion through said color-screen filter to a series of color separation photographic images with light of different colors, developing and fixing said film, converting the metallic silver image to a substantially white image and rendering the emulsion surface of said film substantially black.

7. The method of making a photographic color print to be viewed by reflected light which includes exposing a sensitive film provided with an inner layer of panchromatic emulsion and a sensitive outer layer of a silver salt emulsion in which is embodied a transparent additive colorscreen filter, through said color-screen filter, to a series of color separation photographic images with light of difierent colors, developing and fixin said film, converting the metallic silver image to a substantially white image and applying a substantially black backing to the rear surface of said inner layer.

8. The method of making a photographic color print to be viewed by reflected light which includes exposing a sensitive transparent additive color-screen filter silver salt emulsion layer to a series of color separation photographic images, developing and fixing said emulsion layer, and converting the metallic silver image therein to a substantially white image.

9. The method of making a photographic color print to be viewed by reflected light which includes the successive steps of making black and white color separation negative films of the subject photographed through red, blue and green filters respectively, making black and white color separation positive films from said negatives, exposing a sensitive film provided with an inner layer of panchromatic emulsion and a sensitive outer layer composed of a transparent additive color-screen filter silver salt emulsion in red, yellow and blue colors, through said color-screen filter successively to the said red color separation positive with blue light, to the said blue color separation positive with green light, and to the said green color separation positive with violet light, developing and fixing said film, converting the metallic silver image embedded therein to a substantially white image and mounting said film emulsion side down upon a substantially black backing.

CHARLES SCHE I'TLER. ERICI-I F. T. SCHENK. 

